drm/i915: s/DRM_IRQ_ARGS/int irq, void *arg

I'm official fed up with the yelling and useless indirection.

Let it burn!

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>